Make the process of fixing the integration tests a lot easier

[adrianclay]

What

• Regenerate the expected JSON files in the integration tests. This will make any future changes easier to view, as they won't have formatting changes in them too.
• Consolidate the three "OVERWRITE" variables into one single variable.
• Make the OVERWRITE variable actually overwrite the file.

Why

Should make development a lot easier.

Type of change

• Internal change (non-breaking change with no effect on the functionality affecting end users)

Checklist:

• I have performed a self-review of my code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have updated the Changelog with details of my change in the UNRELEASED section if this change will affect end users
• A corresponding change has been made to the Mapping Documentation repository